1. Field of the Invention
The present invention relates to an image capturing apparatus and a control method for the image capturing apparatus, and more particularly, to an image capturing apparatus for carrying out autofocus control and a control method for the image capturing apparatus.
2. Description of the Related Art
For autofocus (AF) control of video cameras and the like, TV-AF type AF control is widely used in which an in-focus position is detected on the basis of the sharpness (contrast) of image signals generated with the use of an image sensor. Specifically, an AF evaluation value indicating the degree of contrast is generated for image signals captured sequentially while moving a focus lens, and the position of the focus lens at which the contrast reaches its maximum is searched as an in-focus position on the basis of the AF evaluation value.
However, in the case of shooting a person, focusing on the background rather than the person may occur due to the relationship in contrast between the person as a main object and the background.
In order to solve such a problem, image capturing apparatus are known that detect a person and set a focus detection area for the purpose of focusing on the person. For example, image capturing apparatuses which have a face detection function and carry out focus detection for a focus detection area containing a face region (for example, Japanese Patent Laid-Open No. 2006-227080), and image capturing apparatuses which detect a person's eyes and carry out focus detection on the basis of the eyes (for example, Japanese Patent Laid-Open No. 2001-215403) are proposed.
In conventional TV-AF type AF control, high frequency components of image signals are extracted with a filter or the like for use as AF evaluation values. However, the extracted band stays constant regardless of the type of object, and is set wider such that focusing on any object can be carried out.
However, when the band of the extracted high frequency components is wider, needlessly high frequency components will be included depending on the object. On the other hand, while the AF evaluation value is susceptible to the influence of high frequency components, such high frequency components vary significantly with a subtle movement of the object. Therefore, in a case in which high frequency components are extracted which are unnecessary for the object under normal circumstances, the increase and decrease of the unnecessary frequency components may result in inconsistent AF evaluate values, negatively affecting the speed and accuracy of AF.